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About Michael J. Miller

Miller, who was editor-in-chief of PC Magazine from 1991 to 2005, authors this blog for PC Magazine to share his thoughts on PC-related products. No investment advice is offered in this blog. All duties are disclaimed. Miller works separately for a private investment firm which may at any time invest in companies whose products are discussed in this blog, and no disclosure of securities transactions will be made.

Mobile Building Blocks 2014: More Powerful Graphics Architectures

Yesterday, I talked about the CPU architectures from ARM and others that form an integral building block for all of today's mobile processors. Now, I want to look at the options for graphics processors.

If ARM dominates CPU architecture, the graphics architectures used by different processors have now become a much more diverse field, with several options for licensed technologies, including IP from Imagination Technologies, ARM, Vivante, and theoretically Nvidia. Of course, a number of chip makers, notably Qualcomm, use their own proprietary graphics designs; and a number of chip makers use technology from multiple makers depending on the specific product. But how the chip vendors actually use graphics and video technology in the chips is becoming a big differentiator.

Imagination Technologies PowerVR Sets Standards
Imagination Technologies, with its PowerVR family of graphics cores, has been making mobile graphics for a long time and remains the best-known third-party provider, with Apple and Intel among its most visible customers.

A large number of products use the company's PowerVR series 5, including its 5XT extension that adds some capabilities enabling OpenGL ES 3.0 capabilities. For instance, Apple has quietly confirmed that the CPU used in the iPhone 4s, 5, and 5c run Imagination's PowerVR SGX 543 graphics; and the one in the 4th-generation iPad uses PowerVR 554MP4, with the final four indicating it has four graphics cores.

Last year, Imagination announced Power VR series 6, codenamed Rogue, which includes native support for DirectX 10 and Open GL ES 3.0. This was offered with between one and six clusters of graphics, ranging from the G6100 to the top-end 6630.

A number of vendors have announced processors using Series6, including Intel, MediaTek, Allwinner, and reportedly Apple.

This year, the company announced the PowerVR Series6XT GPU, with the GX6650 as its top-of-the-line offering. It uses six unified shading clusters and 192 "cores" - technically arithmetic logic units. (Everyone counts "cores" differently in graphics; effectively, this seems to be Imagination adopting Nvidia's use of the term "core." Previously the company called each collection of units or shading cluster a core.) The company says the chip can produce up to 460.8 16-bit GFLOPS and up to 230.4 32-bit GFLOPS at 600MHz, a very fast result. (Again, like anything in graphics, you should always take these numbers with a grain of salt.) In addition, the company is pushing its PowerVR 2500 Raptor imaging processor and its video solution.

Last week at the Game Developer Conference, Imagination announced an extension to the PowerVR Series6XT with special hardware designed for ray tracing. The GR6500, part of a new family code-named Wizard, will reportedly deliver up to 300 million rays per second along with the GPU's 150 32-bit GFLOPS, the company said. Ray tracing is a method for rendering realistic-looking effects, such as lighting and shadows, reflections and transparency, but real-time ray tracing has traditionally been too computationally intensive for even high-end PCs with the most powerful graphics cards. By combining traditional rasterization with selective ray tracing, Imagination says its hardware will deliver much more realistic games and other 3D applications on mainstream smartphones and tablets.

ARM's Mali Grows More Competitive
Lately, Imagination has faced more competition in the licensed graphics space, particularly in mid-range and low-end phones, as ARM's Mali graphics line has gained more traction. ARM says that in 2013, more than 400 million devices with MALI GPUs shipped, and that it added 23 new licensees. The most well-known processors with such graphics include most models of Samsung's Exynos processors and several new MediaTek chips. (Note that a number of processor makers use graphics from different suppliers in different chips.)

ARM offers a number of Mali cores, in both low- and high-end configurations. The Mali-400 and -450 families are aimed mostly at mass market smartphones, while the Mali-T600 family is aimed more at the high end.

Last fall, ARM introduced its current top end of the line, known as the Mali 760, which can scale to 16 cores (clusters – though again, it's hard to compare these across architectures, as what each developer counts is different), including two 512KB L2 caches, and run at up to 600 MHz. The company says it can produce up to 326 GFLOPS.

Vivante Renews Graphics Push
Vivante doesn't get as much attention, but it's the third largest graphics IP supplier, known mostly for supplying graphics used in all of the processors from Marvell in its PXA and Armada line. But the company seems a bit more aggressive lately, with wins in processors from other companies including HiSilicon (which produces chips for Huawei), Rockchip, Freescale, and Spreadtrum.

The company's current line, known as Vega, includes support for Open GL ES 3.1 and Direct X 11. Vivante says its top-of-the-line offering, called Vega 8X or the GC7000 series, offers 32/64 shader cores (for high and medium precision), a clock speed of up to 800 MHz, and up to 256 (high precision) or 512 (medium precision) GFLOPs. It also claimed to have the smallest core capable of running Open GL ES 3.0, requiring 2.0 mm2 at 28 nm.

Qualcomm, Nvidia Take Unique Approaches
Of course, a variety of the mobile processor makers have their own proprietary graphics technology. Qualcomm offers its Adreno graphics, which it uses in its Snapdragon processors. The top end of this is the new Adreno 420, used in the Snapdragon 805, which Qualcomm says will be 40 percent faster than the graphics in the Snapdragon 800, which ran many of 2013's top-end phones. The 420 adds a variety of new features, including its own hardware tessellation engine, geometry shaders, Direct3D 11 support, and H.265 hardware-accelerated decode for 4K content.

Nvidia just introduced a new version of its Tegra line, called K1, which it said had 192 "CUDA cores" (programmable shaders) and support for standards such as Direct X 11. The company's existing Tegra 4 chip has up to 72 graphics cores. Although Nvidia has said it will license its graphics IP, thus far, no other vendor has announced a chip that uses this.

In both of these cases, I'll discuss them in more detail in an upcoming post about their specific chips.

Even though there are a lot of standard building blocks that go into making mobile processors, the resulting combinations offer a wide range of possibilities.

How the chipmakers take the various CPU options and graphics options, combine these with video and imaging choices, modems, and connectivity, not to mention how they balance concerns such as power and performance, determines the capabilities of the resulting chip, and how well it does. In my next post, I'll look more closely at the specific application processor makers.

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